Registered jacks are usually described under the acronym RJ-XX and are a series of telephone connection interfaces that include a receptacle and plug. These jacks are registered with the U.S. Federal Communications Commission (FCC). They are efficiently designed and have evolved from the various interfaces that were part of the AT&T universal service order code (USOC). The term "registered jack" or "registered jack connector" or simply "jack" is often used in the industry and refers to both a receptacle and/or plug and sometimes just the receptacle. One common telephone registered jack connector is an RJ-11 jack having six conductors, but usually used with four conductors. The RJ-11 registered jack connector is usually used in household or office phone environments and plugged into ordinary "untwisted" wire (often called "flat wire" or "gray satin" wire). Sometimes these jacks connect to "outside" and longer wires commonly referred to as twisted pair wire, which also connect to a telephone company central office or private branch exchange (PBX). The different four wires are typically color coded as a red and green pair and a black and white pair, respectively. The red and green pair of telephone lines usually carry voice or data. On an outside telephone company connection, the black and white pair can be used for low voltage signals, such as phone lights. On a PBX system, on the other hand, the black and white pair could be used for other kinds of signaling commonly used in PBX applications. A computer modem is typically connected to an RJ-11 jack.
One very common type of single line jack used for digital transmission over ordinary phone lines is an RJ-45 jack, which is becoming more common in use. Either untwisted or twisted phone wire can be used with this jack. The RJ-45 jack has eight positions or pins. If a modem, printer or data PBX is connected and a data rate up to 19.2 KBPS desired, untwisted wire can be used. It is possible to obtain faster transmissions when a connection is made via an Ethernet 10 base T network where twisted pair wire is used. Untwisted wire is usually a flat wire similar to common household phone extension wire, while twisted is often round. The RJ-45 jack can be both keyed and unkeyed where the keyed jack has a small bump on its end and the female complements it.
Twisted pair wiring typically dominates the wiring commonly used in facilities having both LAN and telephone wiring. Unshielded twisted pair (UTP) wire is in wide use when 19-26 gauge individual wires in a wire bundle are used. Premises wire is usually 24-26 gauge (AWG with commonly two twists per foot).
The twisting of a telephone wire pair cancels out radiated energy from current flowing in one wire by the radiated energy from the same return current that flows in the return wire of the same pair. Thus, crosstalk is minimized between adjacent pairs of wire. Twisting the individual wires also makes a wire pair less susceptible to external noise because the noise is coupled equally into each wire pair. Thus, noise is canceled out when wires are properly terminated. At voice frequencies, the wire pair would appear to be balanced. Equal energy would be emitted from each wire within the pair to any point outside the pair wires.
Often, the unshielded twisted pair cabling is used in Ethernet and token ring applications. The wires connect to a network interface card, as is well known to those skilled in the art. Four wires are used in a hub to NIC cable. The RJ-45 connectors are commonly used for a UTP connection. In addition to the RJ-45 connectors, a color coding scheme is used for a UTP connection. For example, some UTP category three cables use a solid and striped wire color scheme, such as orange and orange/white, blue and blue/white, green and green/white and brown and brown/white. The solid and striped color combinations are used to determine which pairs of wires must be twisted together in a specific sequence to provide adequate signaling. For example, the wires would be connected to various pins and receiving slots in the jack depending on the end use application. For example, an Ethernet 10 base-T connection could use pins 1 and 2 and 3 and 6, while a token-ring UTP connection could use pins 4 and 5 and 3 and 6.
With the increased use of RJ-45 modular telephone jacks in different applications, it is common now to connect individual wires, such as from a wire bundle, directly into the grooves or slots (i.e., wire receiving areas) of a jack to connect the wire to the conductive pins. This wire insertion process may not be difficult for experienced wire handlers and technicians, who work with the wire bundles and jacks everyday. However, for less experienced users, such as a residential user or handicapped person, the manual placing of individual wires into these jacks can be very difficult.